Growing rod for treating spinal deformities and method for using same

ABSTRACT

An implantable growing rod assembly adapted to be secured along a length of a spine for treating deformities of the spine. The assembly includes a housing, a fixed rod extending along a longitudinal axis away from the housing, and an expansion rod extendible from the housing along the longitudinal axis. A driver assembly is fixed to the housing and adapted to translate the expansion rod along the longitudinal axis.

REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. Ser. No. 16/238,864,filed Jan. 3, 2019 (published as U.S. Pat. Pub. No. 2019-0209211), whichis hereby incorporated by reference in its entireties for all purposes.

FIELD OF THE INVENTION

The present invention relates generally to a growing rod for treatingspinal deformities, and more particularly to a growing rod that can besecured to a spine of a patient and manually extended to grow with thepatient's spine.

BACKGROUND OF THE INVENTION

Scoliosis is a term used to describe any abnormal, sideway curvature ofthe spine. The most common form of scoliosis for patients between theage of 10 and 18 years is termed adolescent idiopathic scoliosis (AIS).Although the particular cause of this type of scoliosis is stillunknown, advancements in the medical field have enabled doctors toincrease the likelihood of successfully treating scoliosis is childrenand adolescents.

Studies have shown that curvatures in the spine progress during therapid growth period of children. Because of this, children sufferingfrom scoliosis are generally recommended by their doctor to undergosurgical treatment to prevent curve progression and to obtain some curvecorrection.

One type of spinal surgery for treating scoliosis in children is the useof implantable rods that allow for continued growth of the spine. One ortwo rods are implanted into the child through the back of the spine. Therods are then secured to the spine above and below the curve using hooksor screws. Because the child will continue to grow after the spinalsurgery, the child will be required to return every few months to havethe rods lengthened to keep up with his/her growth.

There thus exists a need to provide improved growing rods.

SUMMARY OF THE INVENTION

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

The present invention cures some of the deficiencies in the prior art byproviding a growing rod that is less complex and that can be manuallyextended by a user.

The growing rod of the illustrative embodiment of the present inventionis adapted to be subcutaneously implanted and secured along a length ofa spine of a patient. The growing rod comprises a base rod, anextendible rod having a distal portion that is slidably coupled to thebase rod and arranged with a gear rack, and a distraction unit.

The distraction unit provides one or more mechanical elements tofacilitate linear movement of the extendible rod relative to the baserod. In general, the distraction unit comprises: (i) a housing attachedto the base rod, (ii) a rotatable drive interface accessible by anexternal driver from outside of the housing, and (iii) a drive gearmechanism housed within the housing and coupled to the rotatable driveinterface and the gear rack such that rotation of the rotatable driveinterface causes linear movement of the extendible rod through the gearrack.

Because the patient is likely to continue to grow after implantation ofthe growing rod, the patient will be required to return to the doctor(e.g., two months, four months, six months, etc., after each doctor'svisit) to have the growing rod extended in order to keep up with thepatient's growth. This can be accomplished by making a small incision onthe patient's back to access the rotatable drive interface with anexternal driver. The rotatable drive interface is adapted to bephysically coupled to and manually rotated by the external driveremployed by the doctor. As the doctor rotates the rotatable driveinterface in a first direction (e.g., clockwise), it causes linearmovement of the extendible rod through the gear rack. The linearmovement is a result of a gear in the drive gear mechanism cooperatingwith the gear rack to linearly move the extendible rod relative to thebase rod. A latching mechanism housed within the housing is configuredto latch onto the drive gear mechanism to prevent the rotatable driveinterface from being able to rotate in a second direction (e.g.,counter-clockwise) for retracting the extendible rod. The latchingmechanism also provides a means to prevent the drive gear mechanism fromcausing the extendible rod from retracting under pressure of the spine;for example, when the patient is sitting up, standing, walking, etc.

To unlatch the latching mechanism, provided is a rotatable cam interfacearranged on the outside of the housing. The doctor can access therotatable cam interface by using an external cam driver. Rotating therotatable cam interface using the driver causes a cam housed within thehousing to unlatch the latching mechanism from the drive gear mechanism,thereby allowing the doctor to rotate the rotatable drive interface inthe second direction. This feature allows the doctor to fine tune theoverall length of the growing rod if the extendible rod has beenextended too much.

By providing a manually operated implant that is less complex, like thegrowing rod of the illustrative embodiment, fewer elements and movingparts can be used to extend and retract the implant without the need ofa power source.

In an alternative embodiment of the present invention, different typesof gears and gear configurations are employed to extend the extendiblerod relative to the base rod.

In a further alternative embodiment of the present invention, theextendible rod is extended relative to the base rod by means of applyingfluid pressure through a fluid intake coupled to a fluid connection bodyof the growing rod. The fluid pressure enters the connection body andforces a piston forwards to extend the extendible rod.

In yet another alternative embodiment, a growing rod is adapted to beextended by incrementally pushing a toggling switch on the surface of apatient's skin.

In still a further alternative embodiment, an implantable growing rodassembly is adapted to be secured along a length of a spine for treatingdeformities of the spine. The assembly includes a housing, a fixed rodextending along a longitudinal axis away from the housing, and anexpansion rod extendible from the housing along the longitudinal axis. Adriver assembly is fixed to the housing and adapted to translate theexpansion rod along the longitudinal axis.

These advantages of the present invention will be apparent from thefollowing disclosure and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, features, and advantages of the present device willbecome more fully apparent from the following detailed description, theappended claims, and the accompanying drawings in which like referencenumerals identify similar or identical elements.

FIG. 1 is a perspective view of a growing rod in a collapsedconfiguration in accordance with an illustrative embodiment of thepresent invention.

FIG. 2 is a perspective view of the growing rod of FIG. 1 in a fullyextended configuration in accordance with an illustrative embodiment ofthe present invention.

FIG. 3 depicts the outside of a housing of a distraction unit inaccordance with an illustrative embodiment of the present invention.

FIG. 4 depicts the inside of the housing of the distraction unit inaccordance with an illustrative embodiment of the present invention.

FIG. 5A depicts an opening arranged on a base rod of the growing rod inaccordance with an illustrative embodiment of the present invention.

FIG. 5B depicts an opening arranged on the housing of the distractionunit in accordance with an illustrative embodiment of the presentinvention.

FIG. 6 depicts a cam and a latch configuration for allowing anextendible rod of the growing rod to be retracted.

FIG. 7A depicts an extendible rod having a gear train that shows oneside of a compound gear in accordance with an alternative embodiment ofthe present invention.

FIG. 7B depicts the other side of the gear train of FIG. 7A inaccordance with an alternative embodiment of the present invention.

FIG. 8A is a perspective view of a hydraulic growing rod in a collapsedconfiguration in accordance with an alternative embodiment of thepresent invention.

FIG. 8B is a perspective view of the g hydraulic rowing rod of FIG. 8Ain a fully extended configuration in accordance with an alternativeembodiment of the present invention.

FIG. 9 is an exploded view of the fluid connection body, fluid intake,and piston for extending an extendible rod through fluid pressure inaccordance with an alternative embodiment of the present invention.

FIG. 10 is a perspective view of a growing rod in accordance with yetanother alternative embodiment of the present invention.

FIG. 11 depicts the elements that form the growing rod of FIG. 10.

FIG. 12 is a cross-sectional view of the growing rod of FIG. 10.

FIG. 13 depicts the one-way, sliding, sawtooth clutch for extending thegrowing rod of FIG. 10.

FIG. 14 is a top perspective view of an alternative growing rod inaccordance with some embodiments.

FIG. 15 is a top perspective view of the alternative growing rod of FIG.14 with portions of the housing removed.

FIG. 16 is a close up view of the gear set of the alternative growingrod of FIG. 14.

FIG. 17 is a top perspective view of another alternative growing rod inaccordance with some embodiments.

FIG. 18 is a top perspective view of the alternative growing rod of FIG.17 with portions of the housing removed.

FIG. 19 is a close up view of the gear set of the alternative growingrod of FIG. 17.

FIG. 20 is a top perspective view of a growing rod including a magnet inaccordance with some embodiments.

FIG. 21 is a top perspective of the growing rod of FIG. 20 with portionsof the housing removed.

FIG. 22 is a close up view of the gear set of the growing rod of FIG.19.

FIG. 23 is a close up view of a planetary gear of the growing rod ofFIG. 19.

FIG. 24 is a side elevational view of an implantable rod assemblyaccording to an alternative embodiment.

FIG. 25 is an enlarged broken side elevational view of the rod assemblyof FIG. 24.

FIG. 26 is an exploded perspective view of the rod assembly of FIG. 24.

FIG. 27 is an enlarged side elevational view of the rod assembly of FIG.24, with the housing omitted.

FIG. 28 is a side elevational view, in section, of the rod assembly ofFIG. 24, with the extendible rod in a contracted position.

FIG. 29 is a side elevational view, in section, of the rod assembly ofFIG. 24, with the extendible rod in an extended position.

FIG. 30 is a side elevational view of the rod assembly of FIG. 24,showing an exemplary contracted length of the rod assembly.

FIG. 31 is a side elevational view of the rod assembly of FIG. 24,showing an exemplary extended length of the rod assembly.

FIG. 32 is a lower perspective view of two rod assemblies of FIG. 24implanted onto a patient's spinal column.

FIG. 33 is a side elevational view of an implantable rod assemblyaccording to an alternative embodiment.

FIG. 34 is an enlarged broken side elevational view of the rod assemblyof FIG. 33.

FIG. 35 is an exploded perspective view of the rod assembly of FIG. 33.

FIG. 36 is an enlarged side elevational view of the rod assembly of FIG.33, with the housing omitted.

FIG. 37A is a side elevational view, in section, of the rod assembly ofFIG. 33, with the extendible rod in a contracted position.

FIG. 37B is a side elevational view, in section, of the rod assembly ofFIG. 33, with the extendible rod in an extended position.

FIG. 38A is a side elevational view of the rod assembly of FIG. 33,showing an exemplary contracted length of the rod assembly.

FIG. 38B is a side elevational view of the rod assembly of FIG. 33,showing an exemplary extended length of the rod assembly.

FIG. 39 is a lower perspective view of two rod assemblies of FIG. 33implanted onto a patient's spinal column.

FIG. 40 is an exploded perspective view of an implantable rod assemblyaccording to an alternative embodiment.

FIG. 41 is an enlarged side elevational view of the rod assembly of FIG.40, with the housing omitted.

FIG. 42A is a side elevational view, in section, of the rod assembly ofFIG. 40, with the extendible rod in a contracted position.

FIG. 42B is a side elevational view, in section, of the rod assembly ofFIG. 40, with the extendible rod in an extended position.

FIG. 43A is a perspective view of an implantable rod assembly accordingto an alternative embodiment.

FIG. 43B is a side close-up view of a ratchet mechanism of the rodassembly of FIG. 43A.

FIG. 43C is a side close-up view, in section, of the ratchet mechanismof FIG. 43B.

FIG. 43D is a perspective view, in section, of the rod assembly of FIG.43A.

DETAILED DESCRIPTION

In the drawings, like numerals indicate like elements throughout.Certain terminology is used herein for convenience only and is not to betaken as a limitation on the present device. The terminology includesthe words specifically mentioned, derivatives thereof and words ofsimilar import.

The embodiments illustrated below are not intended to be exhaustive orto limit the device to the precise form disclosed. These embodiments arechosen and described to best explain the principle of the device and itsapplication and practical use and to enable others skilled in the art tobest utilize the device.

Reference herein to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connectionwith the embodiment can be included in at least one embodiment of thedevice. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment, nor are separate or alternative embodiments necessarilymutually exclusive of other embodiments. The same applies to the term“implementation.”

As used in this application, the word “exemplary” is used herein to meanserving as an example, instance, or illustration. Any aspect or designdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other aspects or designs. Rather, use ofthe word exemplary is intended to present concepts in a concretefashion.

Additionally, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or”. That is, unless specified otherwise, or clearfrom context, “X employs A or B” is intended to mean any of the naturalinclusive permutations. That is, if X employs A; X employs B; or Xemploys both A and B, then “X employs A or B” is satisfied under any ofthe foregoing instances. In addition, the articles “a” and “an” as usedin this application and the appended claims should generally beconstrued to mean “one or more” unless specified otherwise or clear fromcontext to be directed to a singular form.

Unless explicitly stated otherwise, each numerical value and rangeshould be interpreted as being approximate as if the word “about” or“approximately” preceded the value of the value or range.

The use of figure numbers and/or figure reference labels in the claimsis intended to identify one or more possible embodiments of the claimedsubject matter in order to facilitate the interpretation of the claims.Such use is not to be construed as necessarily limiting the scope ofthose claims to the embodiments shown in the corresponding figures.

It should be understood that the steps of the exemplary methods setforth herein are not necessarily required to be performed in the orderdescribed, and the order of the steps of such methods should beunderstood to be merely exemplary. Likewise, additional steps may beincluded in such methods, and certain steps may be omitted or combined,in methods consistent with various embodiments of the present device.

Although the elements in the following method claims, if any, arerecited in a particular sequence with corresponding labeling, unless theclaim recitations otherwise imply a particular sequence for implementingsome or all of those elements, those elements are not necessarilyintended to be limited to being implemented in that particular sequence.

Also for purposes of this description, the terms “couple,” “coupling,”“coupled,” “connect,” “connecting,” or “connected” refer to any mannerknown in the art or later developed of joining or connecting two or moreelements directly or indirectly to one another, and the interposition ofone or more additional elements is contemplated, although not required.

FIG. 1 shows a growing rod 100 in a collapsed configuration inaccordance with an illustrative embodiment of the present invention. Thegrowing rod comprises: base rod 102, extendible rod 104, and distractionunit 106. Each of these elements that form growing rod 100 can beconstructed from a biocompatible plastic, metal, metal alloy, or acombination thereof. The biocompatible metals and metal alloys can be,for example, and without limitation, titanium, titanium alloy, stainlesssteel, cobalt chrome, or any combination thereof. However, it will beclear to those skilled in the art, after reading this disclosure, how tomake and use alternative embodiments in which some of the elements ofgrowing rod 100 is made from a durable thermoplastic polymer, such aspolyether ether ketone (PEEK).

In accordance with the illustrative embodiment, extendible rod 104 has aproximal portion that is slidably coupled to base rod 102 and arrangedwith a gear rack. The extendible rod may be constructed to have aslightly smaller diameter than that of base rod 102 in order to allowthe extendible rod to telescopically slide in and out of the base rod.It will be clear to those skilled in the art, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which base rod 102 can be adapted to slide in and out ofextendible rod 104.

FIG. 2 shows growing rod 100 in a fully extended configuration inaccordance with an illustrative embodiment of the present invention. Inthis figure, extendible rod 104 has been fully extended relative to baserod 102 in response to a doctor manually rotating a rotatable driveinterface that is arranged on the outside of distraction unit 106. Thedoctor can also fine tune the length of growing rod 100 by retractingextendible rod 104 to a desired distraction length. The doctor canachieve this by manually rotating a rotatable cam interface arranged onthe outside of distraction unit 106 in the opposite direction. Theillustrative embodiment of extendible rod 104 is adapted to allow for aminimum of three and a half years growth before replacement or removalis required. However, it will also be clear to those skilled in the art,after reading this disclosure, how to make and use alternativeembodiments in which extendible rod 104 is adapted for more or less thanthree and a half years growth before replacement or removal is required.These features of the present invention will be described in more detailbelow, with respect to FIGS. 3 and 4.

FIG. 3 is a perspective view of the outside of distraction unit 106 inaccordance with an illustrative embodiment of the present invention. Thedistraction unit comprises: housing 302, rotatable drive interface 304,guide wall 306, recess 308, rotatable cam interface 310, and cover plate312. Each of these elements of distraction unit 106 can be constructedfrom a biocompatible plastic, metal, metal alloy, or combinationthereof. The biocompatible metals and metal alloys can be, for example,and without limitation, titanium, titanium alloy, stainless steel,cobalt chrome, or any combination thereof.

As shown in the figure, rotatable drive interface 304 is arranged on theoutside of housing 302 and is accessible to a doctor via an externaldriver. The rotatable drive interface 304 is hexagon-shaped and isadapted to be received in a correspondingly shaped recess of theexternal driver. The rotatable drive interface 304 can be, for example,and without limitation a 35 mm hex drive interface. Although rotatabledrive interface 304 is depicted as hexagon-shaped, it will be clear tothose skilled in the art, after reading this disclosure, how to make anduse alternative embodiments of the present invention in which rotatabledrive interface 304 can have any shape and size, so long as it can bereceived by the recess of the external driver.

As further shown in the figure, rotatable drive interface 304 issurrounded by guide wall 306, which has a pair of oppositely positionedrecesses 308 arranged on the outer surface of the guided wall. Only onerecess 308 is shown in the figure, but it will be clear to those skilledin the art, after reading this disclosure, that one half of guide wall306 is substantially a mirror image of the other half of the guide wall.In accordance with the illustrative embodiment, each recesses 308 isadapted to receive a correspondingly shaped and sized protrusion, hook,etc., arranged on the external driver. Once received, the externaldriver is locked to guide wall 306 such that lateral movement of theexternal driver is prevented. This mechanism helps prevent the externaldriver from dislodging from rotatable drive interface 304 as the doctoris rotating it. The physical structure of guided wall 306 also has theadded benefit of helping the doctor determine where rotatable driveinterface 304 might be located underneath the skin.

Housing 302 also includes rotatable cam interface 310, which is coupledto a cam housed within housing 302. Although the figure depictsrotatable cam interface 310 as having a slotted head for receiving acorresponding shaped external cam driver, it will be clear to thoseskilled in the art, after reading this disclosure, that rotatable caminterface 310 can have any shape and size, so long as it can receive theexternal cam driver. As will be discussed in more detail below, withreference to FIG. 4, rotating interface 310 causes a cam housed withinhousing 302 to disengage a latch from a drive gear mechanism so that adoctor can retract extendible rod 104.

FIG. 4 is a cross-sectional view of the interior of distraction unit106, thus housing 302, in accordance with an illustrative embodiment ofthe present invention. The interior of the distraction unit comprises:drive gear 402, idler gear 404, pinion 406, cam 408, and latch 410. Likeall of the elements that form growing rod 100, elements 402 to 410 canbe constructed from a biocompatible plastic, metal, metal alloy, orcombination thereof. The biocompatible metals and metal alloys can be,for example, and without limitation, titanium, titanium alloy, stainlesssteel, cobalt chrome, or any combination thereof.

Removing cover plate 312 from housing 302 reveals a drive gear mechanismthat is coupled to rotatable drive interface 304 and gear rack 412. Thegear rack 412 is preferably arranged on a proximal portion of extendiblerod 104, but it will be clear to those skilled in the art, after readingthis disclosure, how to make and use alternative embodiments of thepresent invention in which gear rack 412 is arranged along the length ofextendible rod 104.

In accordance with the illustrative embodiment, the drive gear mechanismcomprises drive gear 402, idler gear 404, and pinion 406. These gearsare coupled to one another as shown in the figure to form a “simple geartrain”. The gear ration between drive gear 402 and pinion 406 ispreferably 2-to-1 (i.e., 2:1 ratio). What this means is that pinion 404has twice as many teeth as drive gear 402. However, those skilled in theart will appreciate after reading this disclosure that distraction unit106 can be configured to have any number of gears and different gearratio ranges without departing from the scope of the invention. Forexample, the gear ratio range can have a lower limit of 1.5 and an upperlimit of 10.

Furthermore, although FIG. 4 only depicts the drive gear mechanism ashaving three gears, it will be clear to those skilled in the art, afterreading this disclosure, how to make and use alternative embodiments ofthe present invention in which the drive gear mechanism has fewer ormore gears than depicted. For example, and without limitation, the drivegear mechanism can have one gear, two gears, ten gears, etc., withoutdeparting from the scope of the present invention. It will also be clearto those skilled in the art that other types of gears and gear trainscould be used without departing from the scope of the present invention.Other types of gears may include, for example, and without limitation,spur gears, helical gears, herringbone gear, face gears, screw gears,etc., or a combination thereof. Other types of gear trains may include,for example, and without limitation, compound gear trains, reverted geartrains, epicyclic gear train, etc., or a combination thereof. Lastly, itwill be clear to those skilled in the art, after reading thisdisclosure, how to make and use alternative embodiments of the presentinvention in which distraction unit 106 can be configured to havedifferent number of gears and different gear ratios without departingfrom the scope of the invention.

As briefly described above, rotatable drive interface 304 is adapted tobe accessed by an external driver from outside of housing 302. Therotatable drive interface is also adapted to be physically coupled toand manually rotated by the external driver for extending and retractingthe extendible rod relative to the base rod. More specifically, rotatinginterface 304 in a first direction (e.g., clockwise) rotates drive gear402 in the same direction. In response to the rotational movement ofdrive gear 402, idler gear 404 will also begin to rotate, but in theopposite direction, while pinion 406 will rotate in the same directionas drive gear 402. Thus, gears 402, 404, and 406 are coupled torotatable drive interface 304 in such a way that rotation of therotatable drive interface causes each of the gears to simultaneouslyrotate. The rotational movement from gears 402, 404, and 406 is thentranslated into linear movement by coupling pinion 406 to gear rack 412.

The coupling between pinion 406 and gear rack 412 is made possible bycoupling housing 302 of distraction unit 106 to base rod 102 as shown inFIGS. 2 and 3. More specifically, and as shown in FIG. 5A, the outersurface of base rod 102 is machined with an opening 502. The opening 502is arranged at a distal portion of base rod 102. The opening 502 canalso be seen in FIG. 4. Similarly, housing 302 has an opening 504arranged on one side of the housing. The opening 504 of housing 302 isshown in FIG. 5B. In accordance with the illustrative embodiment, theteeth 508 of pinion 406 extend slightly outside of opening 504 ofhousing 302. This allows the teeth 508 of pinion 406 to extend throughopening 502 of base rod 102 to engage the teeth 506 of gear rack 412when housing 302 is coupled to base rod 102, thereby forming arack-and-pinion configuration. As discussed above, rotational movementof pinion 406 is translated into linear movement by gear rack 412 suchthat extendible rod 104 can be either extended or retracted, dependingon which direction rotatable drive interface 304 is rotated.

Referring back to FIG. 4, the latching mechanism housed within housing302 is adapted to latch onto a gear of the drive gear mechanism suchthat rotation of rotatable drive interface 304 is prohibited in adirection (e.g., in a counter-clockwise direction) that retractsextendible rod 104. In accordance with the illustrative embodiment, thelatching mechanism comprises latch 410, which is biased to lock thedrive gear mechanism. As shown in the figure, latch 410 is biased tolatch onto and lock idler gear 404. Although latch 410 is biased to lockidler gear 404 in the illustrative embodiment, it will be clear to thoseskilled in the art, after reading this disclosure, how to make and usealternative embodiments of the present invention in which latch 410 isbiased to lock drive gear 402 or pinion 406 instead.

Continuing with the illustrative embodiment, latch 410 is sized andshaped to be received between a pair of adjacent teeth of idler gear404. Latch 410 is spring-loaded in the illustrative embodiment and isadapted to ratchet back and forth as rotatable drive interface 304 isrotated in the clockwise direction for extending rod 104. However, thesize and shape of latch 410 relative to the root/pitch of idler gear 404prevents latch 410 from being able to ratchet back and forth whenrotatable drive interface 304 is rotated in the counter-clockwisedirection for retracting rod 104. That is, latch 410 will not bedislodged from between the pair of adjacent teeth of idler gear 404 whenrotatable drive interface 304 is rotated in a direction that retractsextendible rod 104. This feature of the present invention isadvantageous in that downward pressure exerted on the spine (e.g., whenthe patient is sitting up, standing, etc.) after implantation of growingrod 100 will not cause gears 402, 404, 406 to unintendedly rotate andinadvertently retract rod 104.

FIG. 6 shows latch 410 unlatched from between the pair of adjacent teethof idler gear 404 in accordance with the illustrative embodiment. Tounlatch latch 410, rotatable cam interface 310 is provided. Therotatable cam interface is accessible by an external cam driver fromoutside of housing 302. The rotatable cam interface 310 is coupled tocam 408 such that rotation of the rotatable cam interface causes thelatching mechanism to either prohibit or allow the drive gear mechanismto rotate in a direction that retracts or extends the extendible rod104.

Specifically, rotatable cam interface 310 is adapted to be physicallycoupled to and manually rotated by external cam driver 310 such thatrotation of rotatable cam interface 310 causes a tip of cam 408 toengage or be free from physical contact with latch 410. The rotatablecam interface 310 is rotatable from outside of housing 302 in a firstdirection (e.g., counter-clockwise) until the tip of cam 310 abutsagainst lever 602 of latch 410 and pins it against stopper 604. Thiscauses latch 410 to be unlatched from between the pair of adjacent teethof idler gear 404. This also holds latch 410 in the unlatched positionso that the doctor can rotate interface 304 to retract extendible rod104 to a desired length. After reaching the desired length, the doctorcan use the external cam driver to rotate interface 310 in a seconddirection (e.g., clockwise) to position latch 410 between a pair ofadjacent teeth of idler gear 404, thereby locking gears 402, 404, and406 from rotating in a direction that retracts extendible rod 104.

Having described the elements of growing rod 100 in particular detail,an example of using growing rod 100 will now be described. After growingrod 100 has been implanted into a patient, the patient may be requiredto return to the doctor every few months to have growing rod 100extended to keep up with his/her growth. To extend growing rod 100, thedoctor uses his hands to feel for where distraction unit 106 is located;in particular, where guide wall 306 is located underneath the patient'sskin. Once located, a small incision is made on the patient's back nearguide wall 306. An external driver is inserted through the smallincision and then physically coupled to rotatable drive interface 304from outside of housing 302. Once coupled, the doctor may manuallyrotate rotatable drive interface 304 using the coupled external driver.As discussed above, with respect to FIGS. 3-6, rotating interface 304also rotates drive gear 402, idler gear 404, and pinion 406, since eachof these gears are either physically or indirectly coupled to rotatabledrive interface 304. The rotational movement of these gears is thentranslated into linear movement through the rack-and-pinionconfiguration created by coupling pinion 406 to gear rack 412. Thelinear movement of gear rack 412 causes extendible rod 104 to linearlyextend relative to base rod 102. Likewise, rotating interface 304 in theopposite direction causes extendible rod 104 to linearly retractrelative to base rod 102, as discussed above, with respect to FIGS. 3-6.

It should be noted that “manual” rotation of rotatable drive interface304 includes, for example, and without limitation, physically couplingthe external driver to rotatable drive interface 304 and then having thedoctor manually rotate the physically coupled external driver in aclockwise or counter-clockwise direction. In this embodiment, theexternal driver is similar to, for example, and without limitation, asocket wrench that is not electrically driven.

In alternative embodiments, “manual” rotation of rotatable driveinterface 304 includes, for example, and without limitation, physicallycoupling the external driver to rotatable drive interface 304 and thenactuating one or more buttons to electrically power the physicallycoupled external driver. In this embodiment, a power source provideselectricity of the physically coupled external driver to manually rotateinterface 304.

FIGS. 7A and 7B depict an alternative embodiment of extendible rod 104discussed above. FIG. 7A depicts one side of housing 302 of distractionunit 106 with cover plate 312 removed. Housed within housing 302 in thisalternative embodiment are four gears—namely, drive gear 702, a compoundgear formed by a larger gear 704 having a smaller gear 706 coupled onone side of the larger gear, and pinion 708. The smaller gear 706 isshown in FIG. 7B.

In accordance with this alternative embodiment, drive gear 702 iscoupled to larger gear 704 (as shown in FIG. 7A) and smaller gear 706 iscoupled to pinion 708 (as shown in FIG. 7B). Pinion 708 in turn iscoupled to gear rack 412, as discussed above, with respect to FIGS.3-5B. The gear configuration in this alternative embodiment has, forexample, and without limitation, a gear ratio of 4-to-1 (i.e., 4:1ratio). However, those skilled in the art will appreciate after readingthis disclosure that distraction unit 106 can be configured to havedifferent number of gears and different gear ratios without departingfrom the scope of the invention.

To extend or retract extendible rod 104 relative to base rod 102,rotatable drive interface 304 can be respectively rotated in a clockwiseor a counter-clockwise direction, as discussed above, with respect toFIGS. 3-5B. As interface 304 rotates drive gear 702, the larger gear 704and smaller gear 706 also rotate, but in the opposite direction of drivegear 702. The coupling between smaller gear 706 and pinion 708 causeslinear movement of extendible rod 104 through gear rack 412, asdiscussed above. Although FIGS. 7A and 7B do not depict the latchingmechanism (e.g., latch 410, rotatable cam interface 310, cam 408,stopper 604, etc.) discussed above, those skilled in the art willappreciate that this alternative embodiment can be configured to includethe latching mechanism. The advantage of having a gear train thatincludes a compound gear is the ability to more easily meet thedistraction force for extending extendible rod 104.

FIG. 8A shows a growing rod 800 in a collapsed configuration inaccordance with an alternative embodiment of the present invention. Thegrowing rod comprises: base rod 802, extendible rod 804, fluid connectorbody 806, fluid intake 808, piston 810, spring-loaded ball 812, fluidseals 814, end seal 816, input tube 818, and port 820.

FIG. 8B shows growing rod 800 in a fully extended configuration inaccordance with an alternative embodiment of the present invention. Aswill be discussed in more detail below, with respect to FIG. 9,extendible rod 804 has been fully extended relative to base rod 802 inresponse to fluid pressure being applied through fluid intake 808 toforce piston 812 forwards.

Turning now to FIG. 9, and in accordance with this alternativeembodiment, growing rod 800 is implanted along a spine of a patient andcan be expanded after implantation to keep up with the growth of thepatient. More specifically, growing rod 800 can be expanded by making asmall incision on the patient's back to access an input tube 818arranged on fluid intake 808, which fluid intake is coupled to connectorbody 806 of growing rod 800. Once accessible, a fluid hose coupled to afluid delivery device is connected to input tube 818 of fluid intake808. The fluid delivery device is then operated to apply fluid pressure(e.g., saline fluid, etc.) through fluid intake 808. The fluid pressureexits port 820 and forces piston 812 forwards, thereby extending rod 804relative to base rod 802. Although three fluid seals are shown in thefigures, it will be clear to those skilled in the art, after readingthis disclosure, how to make and use alternative embodiments of thepresent invention in which piston 810 has more or less fluid seals thandepicted. It should also be noted that growing rod 800 has an end seal816 that prevents extendible rod 804 from being able to extend too farand decoupling from connector body 806.

Once extendible rod 804 has reached a desired distraction length,extendible rod 804 will be under load pressure. This load pressure willforce extendible rod 804 to retract backwards on itself. At this time,spring-loaded ball 812 is forced up a ramp arranged within a recess ofon piston 810. This causes ball 812 to press up against the side offluid connector body 806, thereby stopping any further retraction ofextendible rod 804. Once extendible rod 804 has been stopped fromretracting on itself, the fluid pressure can be relieved from an accessport to empty fluid connector body 806 of the fluid pressure.

The design of growing rod 800 is advantageous because it has a smalldiameter and is of minimal design complication. Growing rod 800 is alsoadvantageous because the fluid pressure will not be in effect duringimplantation—that is, fluids and pressure will only be introduced whenextendible rod 804 is being extended relative to base rod 802. From thisdesign, growing rod 800 is able to be a passive growth mechanism. As thespine grows, growing rod 800 can be advanced within the patient withoutthe aid of external manipulation. The fact that growing rod 800 can beboth passive and manipulative (if required) reduces the need ofadditional surgeries for the patient.

FIG. 10 depicts a further alternative embodiment of the presentinvention. Growing rod 1000 comprises: extendible rod 1002, coupling1004, toggling switch 1006, spring 1008, and base rod 1010. Each ofthese elements that form growing rod 1000 can be constructed from abiocompatible plastic, metal, metal alloy, or a combination thereof. Thebiocompatible metals and metal alloys can be, for example, and withoutlimitation, titanium, titanium alloy, stainless steel, cobalt chrome, orany combination thereof. However, it will be clear to those skilled inthe art, after reading this disclosure, how to make and use alternativeembodiments in which some of the elements of growing rod 1000 can bemade from a durable thermoplastic polymer, such as polyether etherketone (PEEK).

In accordance with this alternative embodiment, the outer surface ofextendible rod 1002 is arranged with threads 1030. Preferably, only aportion of the outer surface of extendible rod 1002 is threaded withthreads 1030. However, in other embodiments, the entire length ofextendible rod is arranged with threads 1030. The proximal portion ofextendible rod 1002 is adapted to be received within and threaded intothe distal portion of coupling 1004.

Coupling 1004 has a through-hole for receiving extendible rod 1002 andbase rod 1010. As shown in FIG. 12, the inner surface of the distalportion of coupling 1004 is arranged with threads 1040. These threads ofcoupling 1004 allow extendible rod 1002 to be received within andthreaded into the distal portion of coupling 1004. The inner surface ofthe proximal portion or intermediate portion of coupling 1004 isarranged with a groove 1012. The groove is adapted to receive aretaining ring 1014 coupled to base rod 1010 for preventing the base rodfrom being able to slide in and out of the through-hole of coupling1004.

As further shown in FIGS. 11 and 13, the proximal portion of coupling1004 is arranged with teeth 1050 that are adapted to mesh with the teeth1060 of toggling switch 1006 to form a one-way, sliding, sawtoothclutch. The teeth of coupling 1004 and toggling switch 1006 are chamfershaving a symmetrical sloping edge, as shown in the figures. The slopingedge allows teeth 1050 of coupling 1004 to slide along the sloping edgeof the teeth 1060 arranged on toggling switch 1006. The angle of thesloping edge of the teeth of elements 1004 and 1006 can be, for example,and without limitation, 10°, 45°, 65°, etc. As will be discussed in moredetail below, the one-way, sliding, sawtooth clutch allows coupling 1004to rotate and cause linear movement of extendible rod 1002.

Toggling switch 1006 is arranged with a through-hole for receiving baserod 1010. The inner surface of the through-hole of toggling switch 1006has a cutout that is adapted to receive spring 1008. Toggling switch1006 is also arranged with a first toggle 1016 and a second toggle 1018that can be operated by a user (e.g., a doctor, nurse, etc.) to causelinear movement of extendible rod 1002 relative to coupling 1004.

The distal portion of base rod 1010 is arranged with a groove 1020 forreceiving retaining ring 1014. As discussed above, retaining ring 1014is adapted to prevent base rod 1010 from being able to slide in and outof the through-hole of coupling 1004 when seated within groove 1012. Theproximal portion of base rod 1010 is arranged with a circular protrusionhaving an underside that is adapted to abut against spring 1008.

The method of using growing rod 1000 will now be described. Aftergrowing rod 1000 has been implanted along the spine of a patient, thegrowing rod will need to be periodically extended to keep up with thepatient's growth. Unlike the other embodiments described in thisdisclosure, this alternative embodiment does not require making anyincisions on the patient's back access a mechanism for extending thelength of growing rod 1000. Instead, the doctor can simply use his handsand feel where toggling switch 1006 is located underneath the patient'sskin on his/her back. Once the doctor has located toggling switch 1006,the first toggle 1016 or the second toggle 1018 can be operated by thedoctor to lengthen growing rod 1000. For the purpose of this discussion,and without limitation, the first toggle 1016 will be used to lengthengrowing rod 1000.

More specifically, the doctor can press on the first toggle 1016 one ormore times on the surface of the patient's skin. This pressing actioncauses toggling switch 1006 to incrementally rotate in the samedirection in which the first toggle 1016 is pressed; for example, in aclockwise direction. As toggling switch 1006 incrementally rotates in aclockwise direction, the teeth 1060 of toggling switch 1006 will abutagainst the teeth 1050 of coupling 1004, thereby driving the coupling torotate as well. Because coupling 1004 is threaded to base rod 1002,rotating coupling 1004 in this way causes extendible rod 1002 to backout of the through-hole of the coupling, thus extending the length ofgrowing rod 1000.

However, it should be noted that pressing on the second toggle 1018 willnot cause coupling 1004 to rotate in the opposite direction; in otherwords, a counter-clockwise direction. This is because the teeth 1050 ofcoupling 1004 and the teeth 1060 of toggling switch 1006 cooperativelyform a one-way, sliding, sawtooth clutch. More specifically, as thesecond toggle 1018 is pressed by the doctor, the sloping edge of theteeth 1060 of toggling switch 1006 slide along the sloping edge of theteeth 1050 of coupling 1004. This causes toggling switch 1006 to bepushed away from coupling 1004 and compress against spring 1008. Spring1008 is then compressed against the underside of circular protrusion1022 until the teeth 1060 of toggling switch 1006 is once again meshedwith the teeth 1050 of coupling 1004.

As noted above, this alternative embodiment is advantageous in that noincisions are required to extend the growing rod.

FIG. 14 is a top perspective view of an alternative growing rod inaccordance with some embodiments. The growing rod 1100 is a manuallydriven growing rod that advantageously uses a worm gear to extend thelength of the growing rod. The advantageous of using such a worm gear isthat it prevents inadvertent rotation of any particular gears, therebyreducing the risk of undesired movement of the growing rod.

The growing rod 1100 comprises a fixed rod 1102 and an expansion orextendible rod 1104, wherein the extendible rod 1104 is capable ofextending in length away from the fixed rod 1102. The growing rod 1100further comprises a housing 1112 operably connected to a cover plate1142 for receiving the fixed rod 1102 and/or extendible rod 1104therein. The cover plate 1142 is further designed to house one or moregears as part of a gear set 1106 for causing extension and/or retractionof the extendible rod 1104.

As shown in FIG. 14, the growing rod 1100 comprises a fixed rod 1102 andan extendible rod 1104. In some embodiments, the fixed rod 1102comprises a shaft that is configured to have a fixed length relative tothe housing 1112 and/or cover plate 1142. The fixed rod 1102 comprisesan end cap 1103 that is operably attached to the cover plate 1142. Incontrast, the extendible rod 1104 is configured to have an adjustablelength relative to the housing 1112 and/or cover plate 1142. Theextendible rod 1104 is capable of expansion via rotation of a rotatabledrive interface 1107 in a first direction, and retraction via rotationof the rotatable drive interface 1107 in a second direction opposite thefirst direction. In some embodiments, the extendible rod 1104 comprisesan outer threaded portion (shown as reference numeral 1321 in FIG. 21)that is configured to engage an inner threaded portion of an innerthreaded sleeve 1132. This engagement between the threaded portionsaccommodates lateral movement of the extendible rod 1104 upon rotationof the inner threaded sleeve 1132.

The extendible rod 1104 is received in the hollow shaft of an innerthreaded sleeve 1132 (shown in FIG. 15), which itself is received in thehollow shaft of housing 1112. The housing 1112 comprises a hollow bodywhich advantageously encloses a portion of the extendible rod 1104,thereby protecting it from interference with tissue and other objects inthe body. On a first end of the housing 1112, an extendible rod 1104extends there through. On a second end of the housing 1112, a coverplate 1142 is operably attached to the housing 1112. The cover plate1142 is designed to house and protect a gear set 1106.

In the present embodiment, the gear set 1106 comprises a worm gear set.The worm gear set 1106 comprises a worm in the form of a rotatable driveinterface 1107 that is engaged to worm gear 1108 (shown in FIG. 15).Advantageously, a worm gear helps to hold the position of the growingrod 1100 so that it does not inadvertently retract. Rotation of therotatable drive interface 1107 in a first direction causes rotation ofthe worm gear 1108 to rotate around a longitudinal axis of the growingrod 1100. The rotatable drive interface 1107 is visible through aneyelid 1114 that is formed in the cover plate 1142 of the growing rod1100. In some embodiments, the worm gear 1108 is attached to the innerthreaded sleeve 1132. In some embodiments, the worm gear 1108 is weldedto the inner threaded sleeve 1132. Accordingly, rotation of therotatable drive interface 1107 in a first direction causes the worm gear1108 to rotate, which in turn causes rotation of the inner threadedsleeve 1132. As the inner threaded sleeve 1132 is engaged with theextendible rod 1104 via threading, this causes the extendible rod 1104to translate linearly (e.g., extend or expand). Rotation of therotatable drive interface 1107 in a second direction causes the wormgear 1108 to rotate in the opposite direction, which in turn causeslinear translation of the extendible rod 1104 in an opposite, retracteddirection.

FIG. 15 is a top perspective view of the alternative growing rod of FIG.14 with portions of the housing removed. In addition to the housing1112, the cover plate 1142 has also been removed, thereby exposing thegear set 1106. From this view, one can see the inner threaded sleeve1132 which threadingly engages the threaded portion of the extendiblerod 1104. From this view, one can also see how rotation of the rotatabledrive interface 1106 causes rotation of the worm gear 1108, which inturn causes rotation of the inner threaded sleeve 1132 and translationof the extendible rod 1104.

FIG. 16 is a close up view of the gear set of the alternative growingrod of FIG. 14. The gear set 1106 comprises a worm gear set including aworm in the form of a rotatable drive interface 1106 and a worm gear1108. As shown in this figure, the worm gear 1108 is attached to theinner threaded sleeve 1132 (e.g., via welding). As such, rotation of theworm gear 1108 causes rotation of the inner threaded sleeve 1132, whichthereby causes linear translation of an extendible rod 1104 therein.

In some embodiments, the growing rod 1100 can incorporate a pre-lordosedhousing 1112 and extendible rod 1104. Such a design can also incorporatea flexible inner threaded sleeve 1132. Advantageously, by providing apre-lordosed growing rod 1100, this removes the flexural forces that canincur between the housing 1112 and extendible rod 1104, and can furtherallow for more beneficial contouring of the growing rod 1100 to apatient's anatomy.

In some embodiments, the growing rod 1100 can be affixed to a spine viaone or more bone screws. The growing rod 1100 can be implanted in eitherup or down position and can be used singularly or in pairs. In someembodiments, the growing rod 1100 can be engaged through a smallincision with a hexalobular drive interface. In some embodiments, theworm gear set 1106 provides a reduction ration of 6:1, 8:1, 10:1 ormore. In some embodiments, the worm gear set 1106 provides a reductionratio of 10:1 such that the rotatable drive interface 1107 is rotated 6complete revolutions to achieve 1 mm of growing rod 1100 expansion orcontraction, with the amount of growth based upon a goal measure of 1.8cm to 2.4 cm per year. Advantageously, a surgeon can fine tune theamount of expansion by either increasing or decreasing the amount ofrotations. If a surgeon feels too much distraction has beenincorporated, the growing rod 1100 can be reduced by simply reversingthe direction of the driver.

Advantageously, the growing rod 1100 and previous designs can beimplanted via use of existing pedicle screws. In some embodiments, thegrowing rod 1100 will have the strength of a conventional rod, and canbe adjusted via minimal incision. Per the worm gear set 1106, acontrolled adjustment can be accomplished and distraction forces can beeasily met. In some embodiments, the growing rod 1100 can bemanufactured using a metal, such as steel, cobalt chrome, or titanium.

FIG. 17 is a top perspective view of another alternative growing rod inaccordance with some embodiments. The present growing rod 1200 includesa number of similar features to the growing rod 1100 in FIG. 14,including a fixed rod 1202, an extendible rod 1204, a housing 1212, acover plate 1242, and a worm gear set 1206. In addition to thesefeatures, the growing rod 1200 includes an O-ring cover seal 1219 and asnubber, which will be discussed in more detail below.

The growing rod 1200 comprises a fixed rod 1202 and an extendible rod1204. In some embodiments, the fixed rod 1202 is fixed relative to thehousing 1212 and cover plate 1242, while the extendible rod 1204 ischangeable in length relative to the housing 1212 and cover plate 1242.In some embodiments, the fixed rod 1202 comprises an end cap 1203 thatis operably connected to the cover plate 1242.

Like the growing rod 1100, the cover plate 1242 of the growing rod 1200covers a worm gear set 1206. The worm gear set 1206 comprises arotatable drive interface 1207 that is accessible via a driver throughan eyelid 1214 of the cover plate 1242. Rotation of the rotatable driveinterface 1207 causes rotation of a worm 1209 (shown in FIG. 18). As theworm 1209 is attached to an inner threaded sleeve 1232 (shown in FIG.18), it causes the inner threaded sleeve 1232 to rotate. As theextendible rod 1204 is attached to the inner threaded sleeve 1232 by athreaded engagement, it translates laterally, thereby causing expansionor contraction of the extendible rod 1204.

FIG. 18 is a top perspective view of the alternative growing rod of FIG.17 with portions of the housing removed. From this view, one can see theO-ring cover seal 1219, which extends around the extendible rod 1204.The O-ring cover seal 1219 advantageously helps to seal the housing 1212from the migration of blood or bodily fluids. In addition, the growingrod 1100 can include an optional snubber that helps to control anybacklash from the gear set 1206.

FIG. 19 is a close up view of the gear set of the alternative growingrod of FIG. 17. From this view, one can see the worm gear set 1206 whichincludes the worm in the form of a rotatable drive interface 1207 andthe worm gear 1209. In some embodiments, the worm gear 1209 can includea hex portion that is welded to the inner threaded sleeve 1232, which isnot visible in FIG. 19. As the worm gear 1209 is attached to the innerthreaded sleeve 1232, rotation of the worm gear 1209 causes the innerthreaded sleeve 1232 to rotate, thereby causing translation of theextendible rod 1204.

In some embodiments, the growing rod 1200 can incorporate a pre-lordosedhousing 1212 and extendible rod 1204. Such a design can also incorporatea flexible inner threaded sleeve 1232. Advantageously, by providing apre-lordosed growing rod 1200, this removes the flexural forces that canincur between the housing 1212 and extendible rod 1204, and can furtherallow for more beneficial contouring of the growing rod 1200 to apatient's anatomy.

In some embodiments, the growing rod 1200 can be affixed to a spine viaone or more bone screws. The growing rod 1200 can be implanted in eitherup or down position and can be used singularly or in pairs. In someembodiments, the growing rod 1200 can be engaged through a smallincision with a hexalobular, or hex, drive interface. In someembodiments, the worm gear set 1206 provides a reduction ration of 6:1,8:1, 10:1 or more. In some embodiments, the worm gear set 1206 providesa reduction ratio of 10:1 such that the rotatable drive interface 1207is rotated 6 complete revolutions to achieve 1 mm of growing rod 1200expansion or contraction, with the amount of growth based upon a goalmeasure of 1.8 cm to 2.4 cm per year. Advantageously, a surgeon can finetune the amount of expansion by either increasing or decreasing theamount of rotations. If a surgeon feels too much distraction has beenincorporated, the growing rod 1200 can be reduced by simply reversingthe direction of the driver.

FIG. 20 is a top perspective view of a growing rod including a magnet inaccordance with some embodiments. The growing rod 1300 advantageouslycomprises a combined magnet and worm gear set 1306 that can extend thelength of the growing rod either by an external magnet or via a smallincision with a manual driver. The surgeon thus has the option to extendthe growing rod via the magnet, manual driver or both options, dependingon the needs of a particular patient. In addition to this advantage, theworm gear itself helps to prevent inadvertent rotation (e.g., reverserotation) of the gear set, thereby providing a stable growing rod 1300.In some embodiments, the growing rod 1300 further includes a planetaryreduction gear 1319. The advantage of providing the planetary reductiongear 1319 (shown close up in FIG. 23) is that it provides greater gearreduction per rotation.

The growing rod 1300 comprises a housing 1312 attached to a cover plate1342. The growing rod 1300 further comprises an extendible rod 1304extendible through the housing 1312 and a fixed rod 1302. The extendiblerod 1304 is capable of extending relative to the housing 1312 and coverplate 1342, while the fixed rod 1302 is fixed relative to these twocomponents. The cover plate 1342 encases the gear set 1306, which in thepresent case advantageously includes both a magnet 1308 and a worm gearwith a rotatable drive interface 1307, as will be discussed in moredetail below.

FIG. 21 is a top perspective of the growing rod of FIG. 20 with portionsof the housing removed. From this view, one can see the inner threadedsleeve 1332 that is received in the housing 1312. In some embodiments,the inner threaded sleeve 1332 has a first end and a second end, whereinthe first end is operably attached to the worm gear 1309. In someembodiments, the inner threaded sleeve 1332 is welded to the worm gear1309. In addition, the inner threaded sleeve 1332 includes inner threadsthat engage with a threaded portion 1321 formed on the body 1322 of theextendible rod 1304. Advantageously, the worm gear 1307 can be rotatedeither magnetically or manually via a driver. Rotation of the worm gear1307 causes the inner threaded sleeve 1332 (to which it is attached) tobe rotated. As the extendible rod 1304 is threadingly engaged with theinner threaded sleeve 1332, the extendible rod 1304 will thus rotate andlinearly translate, thus allowing the growing rod 1300 to extend inlength. Rotation of the worm gear 1307 in an opposite direction causesthe extendible rod 1304 to retract.

The gear set 1306 comprises a number of components including a magnet1308, a worm including a rotatable drive interface 1307, a worm gear1309 and a planetary gear 1319. The magnet 1308 is designed to extendradially from a longitudinal axis of the growing rod 1300. The magnet1308 can be engaged via an external magnet that causes rotation of themagnet 1308 and worm 1307. By providing such a magnet, thisadvantageously provides a means for non-invasive growth of the growingrod 1300. The worm including the rotatable drive interface 1307comprises an interface that can be engaged by an external driver (e.g.,a hex driver). By providing such a rotatable drive interface 1307, thisadvantageously provides a means for minimally invasive growth of thegrowing rod 1300. As shown in FIG. 21, the magnet 1308 and the rotatabledrive interface 1307 will rotate together, whether via magnet or manualdriver. As these components rotate, the worm gear 1309 will also berotated around the longitudinal axis of the growing rod 1300. As shownin FIG. 21, the worm gear 1309 can be operably attached to the planetarygear 1319. The planetary gear 1319 advantageously allows for greaterexpansion of the growing rod 1300 with less rotations of the worm gear1309, thereby allowing the surgeon to expend less work during theprocedure. In some embodiments, as shown in FIG. 21, a seal 1329 (e.g.,an O-ring seal) can be received over the extendible rod 1304 to seal thehousing 1312 from any migration of blood or bodily fluids.

FIG. 22 is a close up view of the gear set of the growing rod of FIG.19. From this view, one can see the magnet 1308, the cover plate eyelid1306 housing the worm including the rotatable drive interface 1307, theworm gear 1309 and the planetary gear 1319. The worm gear 1309 and/orplanetary gear 1319 can be attached to the inner threaded sleeve 1332(not shown in FIG. 22), which is threadingly engaged with the extendiblerod 1304.

FIG. 23 is a close up view of a planetary gear of the growing rod ofFIG. 19. The planetary gear 1319 comprises a gear hub 1339 engaged to aseries of miniature gears 1338 a, 1338 b, 1338 c. Rotation of the gearhub 1339 causes the miniature gears 1338 a, 1338 b, 1338 c to rotate,thus causing the overall planetary gear 1319 to rotate.

In some embodiments, the growing rod 1300 can be implanted in either anup or down position and can be used singularly or in pairs. In someembodiments, the magnet 1308 and worm 1306 can be rotated 12, 14, 16, or18 revolutions to achieve 1 mm of rod expansion or contraction, with theamount based upon a goal measure of 1.8 cm to 2.4 cm per year. Theadvantage of the growing rod 1300 is that it is designed to be implantedvia use of bone screws (e.g., pedicle screws) as would a standard rod.The growing rod 1300 can be adjusted non-invasively with the magnet orvia minimal incision. By providing a worm gear 1309 in conjunction witha planetary gear 1319, a controlled adjustment can be accomplished anddistraction forces more easily met. In some embodiments, the growing rod1300 can be made of a metal such as stainless steel, cobalt chrome, ortitanium.

Referring now to FIGS. 24-32, a growing rod assembly 200 (“assembly200”) and its implantation into a spinal assembly will now be discussed.The assembly 200 provides a means for spinal lengthening for pediatricpatients with early-onset idiopathic & neuromuscular scoliosis. Theassembly 200 can provide precise distraction or contraction of the rodfor multiple procedures over an extended period of years and can providegreater overall lengthening of rod than other systems. The assembly 200can accommodate increments and forces to match the growth pattern inscoliosis patients, as well as provide a means of growth through eitherminimally invasive or external manipulation.

As used with assembly 200, the term “proximal” is defined as a directiontoward the free end of the fixed rod 208 and the term “distal” isdefined as a direction toward the free end of the expandable rod 220.

Referring to FIGS. 24-26 and 28, the assembly 200 includes a housing 202in the form of a hollow sleeve. An expansion tube 204 with internalthreads 205 is mounted in the housing 202 and extends the lengththereof. In an exemplary embodiment, the threaded expansion tube 204 isconstructed from a biocompatible titanium alloy.

A housing cap 206 is attached to and is part of the housing 202. A fixedrod 208 extends along a longitudinal axis 201 (shown in FIG. 28)proximally away from the housing 202, such that the housing cap 206 islocated between the housing 202 and the fixed rod 208.

In an exemplary embodiment, the fixed rod 208 is constructed from abiocompatible titanium alloy or any other suitable biocompatiblematerial. The fixed rod 208 has a distal end 254 (e.g., a conical distalend 254) that is fixedly connected to the housing cap 206, an elongatebody 207 (e.g., a long 4.75 mm diameter cylindrical body 207), and aproximal end 209 (e.g., a pointed proximal tip 209). In an exemplaryembodiment, the fixed rod 208 can be laser welded to the housing cap 206or may be otherwise suitably connected or attached. The body 207 locksinto any standard pedicle screw 60. For example, the body 207 may becombined with a pedicle screw 60 that accepts 4.75 mm diameter rods (seeFIG. 32). The pointed proximal tip 209 allows the fixed rod 208 totunnel through tissue when the rod 208 is being passed through thepatient during implantation.

As shown in FIG. 26, the housing cap 206 includes first and secondportions 206 a, 206 b that fit together with a worm drive 242 rotatablymounted between the portions 206 a, 206 b. In an exemplary embodiment,the housing 202 and the housing cap 206 are both made of biocompatibletitanium alloy that are laser welded together to align and protect theinternal components. It is contemplated, however, that suitablematerials and modes of connection or attachment may be used. Each of thehousing cap portions 206 a, 206 b has a through opening 207 a, 207 b,respectively, formed therein to allow access to either side of the wormdrive 242.

Referring to FIG. 28, a keyed bushing 210 is located in the housing 202at a distal end 212 of the housing 202. The bushing 210 includes acentral body portion 214 that is surrounded by a peripheral flange 216.A keyway 218 (shown in FIG. 26), for example, in the form of a flatsurface is formed through the length of the bushing 210. In an exemplaryembodiment, the bushing 210 can be constructed from biocompatible PEEKor other suitable materials and also functions to reduce friction andprevent wear between an expansion rod 220 and the housing 202.

The expansion rod 220 is extendible through and from the housing 202along a longitudinal axis 201. A distal end portion 221 of the expansionrod 220 is adapted to extend outwardly from the distal end 212 of thehousing 202. As shown in FIG. 28, the distal end portion 221 has acylindrical cross-section diameter D1. In an exemplary embodiment, D1 isabout 4.75 mm in order to accommodate commercially available pediclescrews that accept 4.75 mm diameter rods (see FIG. 32). Although it iscontemplated that D1 may be of any suitable diameter to mate with acorresponding pedicle screw system. The distal end portion 221 islocated outside the housing 202 and has a pointed tip 223 (shown in FIG.25) that allows the tip 223 to tunnel through tissue when the expansionrod 220 is being passed through the patient during implantation.

The expansion rod 220 has a threaded proximal end portion 222 that isthreadingly engaged with the threads 205 of the internally threadedexpansion tube 204. The proximal end portion 222 has a larger diameterthan the opening in the bushing 214 so that, when the expansion rod 220is fully extended, as shown in FIG. 29, the bushing 214 retains theproximal end portion 222 in the housing 202.

A central body portion 224 extends between the proximal end portion 222and the distal end portion 221. In a fully contracted position, as shownin FIG. 28, at least a portion of the central body portion 224 extendsdistally of the housing 202. The central body portion 224 has a diameterD2, larger than D1. The larger diameter D2 accommodates a mating key226, for example, in the form of a flat surface (see FIG. 26) thatengages the keyway 218 in the bushing 210 to prevent rotation of theexpansion rod 220 as the expansion rod 220 extends out of or contractsinto the housing 202. Therefore, as the internally threaded expansiontube 204 rotates, the threaded connection between the internallythreaded expansion tube 204 and the threaded proximal end portion 222 ofthe expansion rod 220 causes the expansion rod 220 to translatelongitudinally along the longitudinal axis 201.

Referring to FIG. 28, a driver assembly is disposed in the housing 202and the housing cap 206 and is adapted to translate, or extend, theexpansion rod 220 along the longitudinal axis 201 in a distal directionfrom the hollow housing 202.

In an exemplary embodiment, the driver assembly comprises a gearmechanism. Further, in an exemplary embodiment, the gear mechanismcomprises a right-angle drive gear assembly. In an exemplary embodiment,the right-angle drive assembly comprises a worm gear assembly 240 havinga worm drive 242 and a worm gear output 244 rotatable about thelongitudinal axis 201. As shown in FIG. 28, the worm gear assembly 240is located in the housing cap 206 between the housing 202 and the fixedrod 208.

The worm drive 242 is mounted in the housing cap 206 and is supported byworm bushings 246, 248 (shown in FIG. 26), such that one of the wormbushings 246, 248 is mounted on either side of the worm drive 242. In anexemplary embodiment, the worm bushings 246, 248 are constructed frombiocompatible PEEK or other suitable material and are used to reducefriction and prevent wear when rotating the worm drive 242. In anexemplary embodiment, the worm drive 242 has a hexalobular driveinterface 243 such that a corresponding Torx® wrench driver 70 (shown inFIG. 32) can be used to rotate the worm drive 242. It is contemplatedthat other suitable drive interfaces 243 and drivers 70 may be selected.

The worm gear output 244 has a proximal end 250 that is rotatablysupported by an output gear bushing 252. The output gear bushing 252 ismounted in the distal end 254 of the fixed rod 208, as shown in FIG. 28.The output gear bushing 252 can be constructed from biocompatible PEEKor other suitable material. The gear bushing 252 serves to align theworm gear output 244 with the worm drive 242, reduce friction, andprevent wear between the gear output 244 and the fixed rod 208.

The worm gear output 244 has a distal end 256 that extends into and isfixedly connected to the internally threaded expansion tube 204, such asvia a connecting pin 258. In an exemplary embodiment, the connecting pin258 is constructed from a biocompatible titanium alloy or other suitablematerial. The expansion tube 204 is connected to the worm gear output244 such that the expansion tube 204 rotates with the worm gear output244, thereby translating the expansion rod 220 along the longitudinalaxis 201 as the worm gear output 244 rotates, to extend or contract theexpansion rod 220 from or into the housing 204 such that the assembly200 expands or contracts in length, depending on the direction ofrotation of the worm drive 242.

The worm gear assembly 240 allows a surgeon to turn the worm drive 242,which causes the expandable rod 220 to extend distally from the housing202. In an exemplary embodiment, the worm drive 242 and the worm gearoutput 244 are both made of biocompatible cobalt chrome molybdenumalloy, and are designed with a pitch angle such that the worm drive 242is able to drive the worm gear output 244, but not the reverse.Friction, as well as the pitch angle, between the worm drive 242 and theworm gear output 244 prevents the worm gear output 244 from rotating theworm drive 242. This feature is known as a self-locking feature and isuseful to prevent the expansion rod 220 from expanding or contractingwhile under forces from the patient's spine without directly engagingthe worm drive 242.

In some embodiments, as shown in FIG. 32, the assembly 200 can beaffixed to a spine 50 via one or more pedicle screws 60. The pediclescrews 60 may be in the form of fasteners having a tulip or couplingbody such as those described in U.S. Pat. No. 9,750,542, which isincorporated by reference herein. The assembly 200 can be implanted ineither up or down position and can be used singularly or in pairs. Insome embodiments, the assembly 200 can be engaged through a smallincision with the drive interface 243 (e.g., hexalobular drive interface243). In some embodiments, the worm gear assembly 240 provides areduction ration of 6:1, 8:1, 10:1 or more. In some embodiments, theworm gear assembly 240 provides a reduction ratio of 10:1 such that forevery 10 revolutions of the worm drive 242, the worm gear output 244rotates one complete revolution. In an exemplary embodiment, the wormdrive 242 is rotated about six (6) complete revolutions to achievebetween about 1 mm and 1.25 mm of expansion or contraction of theexpansion rod 220 from the housing 202, with the amount of growth basedupon a goal measure of 1.8 cm to 2.4 cm per year. Advantageously, asurgeon can fine tune the amount of expansion by either increasing ordecreasing the amount of rotations. This allows the surgeon to expandthe expansion rod 220 against large forces caused by the deformity. If asurgeon feels too much distraction has been incorporated, the assembly200 can be reduced by simply reversing the direction of the worm drive242.

Advantageously, the assembly 200 can be implanted via use of existingpedicle screws 60. As shown in FIG. 32, two pedicle screws 60 are usedat either end of the assembly 200 on the fixed rod 208 and the expansionrod 220 to secure the assembly 200 to a patient's spinal column 50.After implantation, the assembly 200 is engaged through a small incisionvia the drive interface 243 of the worm drive 242 with the specifieddriver 70.

The assembly 200 can be implanted at any position along the spinalcolumn 50 with the expansion rod 220 either caudal or cephalad and canbe used singularly or in pairs (as shown in FIG. 32) depending onsurgeon discretion. The length of the expansion rods 220 are oversizedto allow the surgeon to cut, bend, and customize the expansion rod 220depending on patient anatomy. The assembly 200 is designed to allow foran estimated minimum of 5 years of growth before replacement or removalis required. As shown in FIG. 30, in an exemplary embodiment, theassembly 200 is 600 mm long with the expansion rod 220 in a fullyretracted position, and as shown in FIG. 31, in an exemplary embodiment,the assembly 200 is 660 mm long with the expansion rod 220 in a fullyextended position, allowing for up to 60 mm of growth of the patient.

In some embodiments, the assembly 200 will have the strength of aconventional rod, and can be adjusted via minimal incision. By using theworm gear assembly 240, a controlled adjustment can be accomplished anddistraction forces can be easily met. In some embodiments, the assembly200 can be manufactured using a metal, such as steel, cobalt chrome, ortitanium or other suitable biocompatible materials.

Referring now to FIGS. 33-39, a growing rod assembly 3300 (“assembly3300”) and its implantation into a spinal assembly will now bediscussed. The assembly 3300 provides a means for spinal lengthening forpediatric patients with early-onset idiopathic & neuromuscularscoliosis. The assembly 3300 can provide precise distraction orcontraction of the rod for multiple procedures over an extended periodof years and can provide greater overall lengthening of rod than othersystems. The assembly 3300 can accommodate increments and forces tomatch the growth pattern in scoliosis patients, as well as provide ameans of growth through either minimally invasive or externalmanipulation.

As used with assembly 3300, the term “proximal” is defined as adirection toward the free end of the fixed rod 3308 and the term“distal” is defined as a direction toward the free end of the expandablerod 3320.

Referring to FIGS. 33-35 and 37A, the assembly 3300 includes a housing3302 in the form of a hollow sleeve. An expansion tube 3304 withinternal threads 305 is mounted within the housing 3302 and extends thelength thereof. In an exemplary embodiment, the threaded expansion tube3304 is constructed from a biocompatible titanium alloy.

A housing cap 4406 is attached to and is part of the housing 4402. Afixed rod 4408 extends along a longitudinal axis 301 (shown in FIG. 37A)proximally away from the housing 3302, such that the housing cap 3306 islocated between the housing 3302 and the fixed rod 3308.

In an exemplary embodiment, the fixed rod 3308 is constructed from abiocompatible titanium alloy or any other suitable biocompatiblematerial. The fixed rod 3308 has a distal end 3354 (e.g., a conicaldistal end 3354) that is fixedly connected to the housing cap 3306, anelongate body 3307 (e.g., a long 4.75 mm diameter cylindrical body3307), and a proximal end 3309 (e.g., a pointed proximal tip 3309). Inan exemplary embodiment, the fixed rod 3308 can be laser welded to thehousing cap 3306 or may be otherwise suitably connected or attached. Thebody 3307 locks into any standard pedicle screw 60. For example, thebody 3307 may be combined with a pedicle screw 60 that accepts 4.75 mmdiameter rods (see FIG. 39). The pointed proximal tip 3309 allows thefixed rod 3308 to tunnel through tissue when the rod 3308 is beingpassed through the patient during implantation.

As shown in FIG. 35, the housing cap 3306 includes first and secondportions 3306A, 3306B that fit together with a bevel pinion gear 3342rotatably mounted between the portions 3306A, 3306B. In an exemplaryembodiment, the housing 3302 and the housing cap 3306 are both made ofbiocompatible titanium alloy that are laser welded together to align andprotect the internal components. It is contemplated, however, thatsuitable materials and modes of connection or attachment may be used.Each of the housing cap portions 3306A, 3306B has a through opening3307A, 3307B, respectively, formed therein to allow access to eitherside of the bevel pinion gear 3342.

Referring to FIG. 37A, a keyed bushing 3310 is located in the housing3302 at a distal end 3313 of the housing 3302. The bushing 3310 issubstantially similar to the bushing 210 described above. A keyway 3318(shown in FIG. 35), for example, in the form of a flat surface is formedthrough the length of the bushing 3310. In an exemplary embodiment, thebushing 3310 can be constructed from biocompatible PEEK or othersuitable materials and also functions to reduce friction and preventwear between an expansion rod 3320 and the housing 3302.

The expansion rod 3320 is extendible through and from the housing 3302along a longitudinal axis 301. A distal end portion 3321 of theexpansion rod 3320 is adapted to extend outwardly from the distal end3313 of the housing 3302. As shown in FIG. 37A, the distal end portion3321 has a cylindrical cross-section diameter of about 4.75 mm in orderto accommodate commercially available pedicle screws that accept 4.75 mmdiameter rods (see FIG. 39). However, it is contemplated that thediameter of the distal end portion 3321 may be any suitable diameter tomate with a corresponding pedicle screw system. The distal end portion3321 is located outside the housing 3302 and has a pointed tip 3323(shown in FIGS. 33 and 34) that allows the tip 3323 to tunnel throughtissue when the expansion rod 3320 is being passed through the patientduring implantation.

The expansion rod 3320 has a threaded proximal end portion 3312 that isthreadingly engaged with the internal threads 305 of the expansion tube3304. The proximal end portion 3312 has a larger diameter than theopening in the bushing 3310 so that, when the expansion rod 3320 isfully extended, as shown in FIG. 37B, the bushing 3310 retains theproximal end portion 3312 in the housing 3302.

A central body portion 3324 extends between the proximal end portion3312 and the distal end portion 3321. In a fully contracted position, asshown in FIG. 37A, at least a portion of the central body portion 3324extends distally of the housing 3302. In some embodiments, the centralbody portion 3324 may have a diameter larger than the diameter of thedistal end portion 3321. The larger diameter is configured toaccommodate a mating key 3326, for example, in the form of a flatsurface (see FIG. 35) that engages the keyway 3318 in the bushing 3310to prevent rotation of the expansion rod 3320 as the expansion rod 3320extends out of or contracts into the housing 3302. Therefore, as theinternally threaded expansion tube 3304 rotates, the threaded connectionbetween the internally threaded expansion tube 3304 and the threadedproximal end portion 3312 of the expansion rod 3320 causes the expansionrod 3320 to translate longitudinally along the longitudinal axis 301.

Referring to FIG. 37A, a driver assembly is disposed in the housing 3302and the housing cap 3306 and is adapted to translate, or extend, theexpansion rod 3320 along the longitudinal axis 301 in a distal directionfrom the hollow housing 3302.

In an exemplary embodiment, the driver assembly comprises a gearmechanism. Further, in an exemplary embodiment, the gear mechanismcomprises a right-angle drive gear assembly. In an exemplary embodiment,the right-angle drive assembly comprises a bevel pinion gear 3342 and abevel output gear 3344 rotatable about the longitudinal axis 301. Asshown in FIG. 37A, the gear assembly is located in the housing cap 3306between the housing 3302 and the fixed rod 3308. The pinion gear 3342 isdisposed perpendicularly to the output gear 3344.

The bevel pinion gear 3342 is mounted in the housing cap 3306 and issupported by pinion bushings 3346, 3348 (shown in FIG. 35), such thatone of the pinion bushings 3346, 3348 is mounted on either side of thebevel pinion gear 3342. In an exemplary embodiment, the pinion bushings3346, 3348 are constructed from biocompatible PEEK or other suitablematerial and are used to reduce friction and prevent wear when rotatingthe pinion gear 3342. In an exemplary embodiment, the pinion gear 3342has a hexalobular drive interface 3343 such that a corresponding Torx®wrench driver 70 (shown in FIG. 39) can be used to rotate the piniongear 3342. It is contemplated that other suitable drive interfaces 3343and drivers 70 may be selected.

A bevel gear bushing 3352 is disposed between the output gear 3344 andthe housing 3302. The bevel gear bushing 3352 can be constructed frombiocompatible PEEK or other suitable material. The bevel gear bushing3352 serves to align the gear output 3344 with the pinion gear 3342,reduce friction, and prevent wear between the output gear 3344 and thehousing 3302.

The bevel output gear 3344 forms an end (i.e., is integral with) theinternally threaded expansion tube 3304. As a result, the expansion tube3304 rotates with the bevel output gear 3344, thereby translating theexpansion rod 3320 along the longitudinal axis 301 as the bevel outputgear 3344 rotates, to extend or contract the expansion rod 3320 from orinto the housing 3304 such that the assembly 3300 expands or contractsin length, depending on the direction of rotation of the pinion gear3342.

The bevel gear assembly allows a surgeon to turn the pinion gear 3342,which causes the expandable rod 3320 to extend distally from the housing3302. In an exemplary embodiment, the pinion gear 3342 and the beveloutput gear 3344 are both made of biocompatible titanium alloy (e.g.TAV), and are designed with a pitch angle such that the pinion gear 3342is able to drive the bevel output gear 3344.

In some embodiments, as shown in FIG. 39, the assembly 3300 can beaffixed to a spine 50 via one or more pedicle screws 60. The pediclescrews 60 may be in the form of fasteners having a tulip or couplingbody such as those described in U.S. Pat. No. 9,750,542, which isincorporated by reference herein. The assembly 3300 can be implanted ineither up or down position and can be used singularly or in pairs. Insome embodiments, the assembly 3300 can be engaged through a smallincision with the drive interface 3343 (e.g., hexalobular driveinterface 3343). In some embodiments, the bevel gear assembly provides areduction ration of 1:0.75 or more. In some embodiments, the bevel gearassembly provides a reduction ratio of 1:0.75 such that for every fullrevolution of the pinion gear 3342, the bevel output gear 3344 rotates0.75 revolutions. In an exemplary embodiment, the ratio of the pinionteeth to the bevel gear teeth is 15:20. In an exemplary embodiment, thepinion gear 3342 is rotated about one (1) complete revolution to achievebetween about 1 mm and 1.25 mm of expansion or contraction of theexpansion rod 3320 from the housing 3302, with the amount of growthbased upon a goal measure of 1.8 cm to 2.4 cm per year. Advantageously,a surgeon can fine tune the amount of expansion by either increasing ordecreasing the amount of rotations. This allows the surgeon to expandthe expansion rod 3320 against large forces caused by the deformity. Ifa surgeon feels too much distraction has been incorporated, the assembly3300 can be reduced by simply reversing the direction the pinion gear3342 is turned.

Advantageously, the assembly 3300 can be implanted via use of existingpedicle screws 60. As shown in FIG. 39, two pedicle screws 60 are usedat either end of the assembly 3300 on the fixed rod 3308 and theexpansion rod 3320 to secure the assembly 3300 to a patient's spinalcolumn 50. After implantation, the assembly 3300 is engaged through asmall incision via the drive interface 3343 of the pinion gear 3342 withthe specified driver 70.

The assembly 3300 can be implanted at any position along the spinalcolumn 50 with the expansion rod 3320 either caudal or cephalad and canbe used singularly or in pairs (as shown in FIG. 39) depending onsurgeon discretion. The length of the expansion rods 3320 are oversizedto allow the surgeon to cut, bend, and customize the expansion rod 3320depending on patient anatomy. The assembly 3300 is designed to allow foran estimated minimum of 5 years of growth before replacement or removalis required. As shown in FIG. 38A, in an exemplary embodiment, theassembly 3300 is 600 mm long with the expansion rod 3320 in a fullyretracted position, and as shown in FIG. 38B, in an exemplaryembodiment, the assembly 3300 is 660 mm long with the expansion rod 3320in a fully extended position, allowing for up to 60 mm of growth of thepatient.

In some embodiments, the assembly 3300 will have the strength of aconventional rod, and can be adjusted via minimal incision. By using thebevel gear assembly, a controlled adjustment can be accomplished anddistraction forces can be easily met. In some embodiments, the assembly3300 can be manufactured using a metal, such as steel, cobalt chrome, ortitanium or other suitable biocompatible materials. The use of a bevelgear assembly as described also advantageously provides more low profileassembly compared with other assemblies. For example, if the surgeondesires to implant an assembly with as low a profile as possible, theassembly 3300 provides a lower profile than the assembly 200 due to theutilization of a bevel gear assembly as opposed to a worm gear assemblybecause the housing required for the bevel gear assembly (See FIG. 34).is smaller than the housing required for the worm gear assembly (SeeFIG. 25).

Referring now to FIGS. 40-42B, a growing rod assembly 4400 (“assembly4400”) in accordance with embodiments of the present disclosure and itsimplantation into a spinal assembly will now be discussed. The assembly4400 is substantially similar to the assembly 3300 discussed above. Assuch, a discussion of many of the similar aspects will be limited herefor brevity.

Referring to FIGS. 40-42B, the assembly 4400 includes a housing 4402 inthe form of a hollow sleeve. An expansion tube 4404 with internalthreads 4405 is mounted within the housing 4402 and extends the lengththereof. In an exemplary embodiment, the threaded expansion tube 4404 isconstructed from biocompatible polyether ether ketone (PEEK) toadvantageously reduce metallic wear debris resulting from metal on metalcontact and improve the imaging capability of the assembly 4400.

A housing cap 4406 is attached to and is part of the housing 4402. Afixed rod 4408 extends along a longitudinal axis 4401 (shown in FIG.42A) proximally away from the housing 4402, such that the housing cap4406 is located between the housing 4402 and the fixed rod 4408.

In an exemplary embodiment, the fixed rod 4408 is constructed from abiocompatible titanium alloy or any other suitable biocompatiblematerial. The fixed rod 4408 has a distal end 4454 (e.g., a conicaldistal end 4454) that is fixedly connected to the housing cap 4406, anelongate body 4407 (e.g., a long 4.75 mm diameter cylindrical body4407), and a proximal end 4409 (e.g., a pointed proximal tip 4409).

As shown in FIG. 40, the housing cap 4406 includes first and secondportions 4406A, 4406B that fit together with a bevel pinion gear 4442rotatably mounted between the portions 4406A, 4406B. In an exemplaryembodiment, the housing 4402 and the housing cap 4406 are both made ofbiocompatible titanium alloy that are laser welded together to align andprotect the internal components. It is contemplated, however, thatsuitable materials and modes of connection or attachment may be used.Each of the housing cap portions 4406A, 4406B has a through opening4407A, 4407B, respectively, formed therein to allow access to eitherside of the bevel pinion gear 4442.

Referring to FIG. 42A, a keyed bushing 4410 is located in the housing4402 at a distal end 4413 of the housing 4402. The bushing 4410 issubstantially similar to the bushing 3310 described above. A keyway 4418(shown in FIG. 40), for example, in the form of a flat surface is formedthrough the length of the bushing 4410. In an exemplary embodiment, thebushing 4410 can be constructed from biocompatible PEEK or othersuitable materials and also functions to reduce friction and preventwear between an expansion rod 4420 and the housing 4402.

The expansion rod 4420 is extendible through and from the housing 4402along a longitudinal axis 4401. A distal end portion 4421 of theexpansion rod 4420 is adapted to extend outwardly from the distal end4413 of the housing 4402. As shown in FIG. 42A, the distal end portion4421 has a cylindrical cross-section diameter of about 4.75 mm in orderto accommodate commercially available pedicle screws that accept 4.75 mmdiameter rods. However, it is contemplated that the diameter of thedistal end portion 4421 may be any suitable diameter to mate with acorresponding pedicle screw system. The distal end portion 4421 islocated outside the housing 4402 and has a pointed tip similar to thepointed tip 3323 shown in FIGS. 33 and 34 that allows the tip to tunnelthrough tissue when the expansion rod 4420 is being passed through thepatient during implantation.

The expansion rod 4420 has a threaded proximal end portion 4412 that isthreadingly engaged with the internal threads 4405 of the expansion tube4404. The proximal end portion 4412 has a larger diameter than theopening in the bushing 4410 so that, when the expansion rod 4420 isfully extended, as shown in FIG. 42B, the bushing 4410 retains theproximal end portion 4412 in the housing 4402.

A central body portion 4424 extends between the proximal end portion4412 and the distal end portion of the expansion rod 4420. In a fullycontracted position, as shown in FIG. 42A, at least a portion of thecentral body portion 4424 extends distally of the housing 4402. In someembodiments, the central body portion 4424 may have a diameter largerthan the diameter of the distal end portion 4421. The larger diameter isconfigured to accommodate a mating key 4426, for example, in the form ofa flat surface (see FIG. 40) that engages the keyway 4418 in the bushing4410 to prevent rotation of the expansion rod 4420 as the expansion rod4420 extends out of or contracts into the housing 4402. Therefore, asthe internally threaded expansion tube 4404 rotates, the threadedconnection between the internally threaded expansion tube 4404 and thethreaded proximal end portion 4412 of the expansion rod 4420 causes theexpansion rod 4420 to translate longitudinally along the longitudinalaxis 4401.

Referring to FIG. 42A, a driver assembly is disposed in the housing 4402and the housing cap 4406 and is adapted to translate, or extend, theexpansion rod 4420 along the longitudinal axis 4401 in a distaldirection from the hollow housing 4402.

In an exemplary embodiment, the driver assembly comprises a gearmechanism. Further, in an exemplary embodiment, the gear mechanismcomprises a right-angle drive gear assembly. In an exemplary embodiment,the right-angle drive assembly comprises a bevel pinion gear 4442 and abevel output gear 4444 rotatable about the longitudinal axis 4401. Insome embodiments, the bevel output gear 4444 is press fit into theexpansion tube 4404 such that the output gear 4444 and the expansiontube 4404 turn together. In some embodiments, the output gear 4444 andthe expansion tube 4404 may alternatively be formed as one piece. Asshown in FIG. 42A, the gear assembly is located in the housing cap 4406between the housing 4402 and the fixed rod 4408. The pinion gear 4442 isdisposed perpendicularly to the output gear 4444.

The bevel pinion gear 4442 is mounted in the housing cap 4406 and issupported by pinion bushings 4446, 4448 (shown in FIG. 35), such thatone of the pinion bushings 4446, 4448 is mounted on either side of thebevel pinion gear 4442. In an exemplary embodiment, the pinion bushings4446, 4448 are constructed from biocompatible PEEK or other suitablematerial and are used to reduce friction and prevent wear when rotatingthe pinion gear 4442. In an exemplary embodiment, the pinion gear 4442has a hexalobular drive interface 4443 (similar to pinion gear 3342described above). It is contemplated that other suitable driveinterfaces 4443 and drivers may be selected. In some embodiments, thepinion gear 4442 may have teeth on both the upper and lower ends of thepinion gear, as depicted in FIGS. 40-42B. Utilizing teeth disposed atboth ends of the pinion gear 4442 advantageously divides the load on theassembly 4400 between both sets of teeth when the assembly is implantedin a patient.

In some embodiments, a wave washer 4449 may be disposed between one ofthe pinion bushings 4446, 4448 and the housing 4402 to exert an upwardforce on the pinion gear 4442. The wave washer 4449 advantageously actsas a locking mechanism to undesired back drive when the assembly 4400 isimplanted in a patient. The pinion gear 4442 has enough room within thehousing 4402 and housing cap 4406 to translate along its own axis. In aneutral/locked state, the wave washer 4449 pushes the pinion gear 4442upward such that the lower set of teeth of the pinion gear 4442 meshwith the teeth of the output gear 4444 while the upper set of teethsimultaneously remain engaged with the teeth of the output gear 4444 aswell. As a result, the pinion and output gears 4442, 4444 are preventedfrom turning (i.e., are locked). As noted above, the patient's load isnow distributed between both sets of teeth. To unlock the gear assembly,a surgeon inserts a driver into the drive interface 4443 and applies alight downward force, thus flattening the wave washer 4449, moving thepinon gear 4442 downward, and disengaging the lower set of teeth of thepinion gear 4442 from the teeth of the output gear 4444. As a result,the gear assembly is allowed to turn freely. When the surgeon removesthe driver, the wave washer 4449 pushes the pinion gear 4442 upwardagain to reengage the lower set of teeth with the teeth of the outputgear 4444, thus locking the gear assembly again. As a result, anautomatic locking mechanism is advantageously provided to ensure theassembly maintains its desired length after being implanted in a patientand expanded to the desired length.

A bevel gear 4452 is disposed between the output gear 4444 and a collar4447 formed at a proximal portion of the expansion tube 4404. In someembodiments, and as shown in FIGS. 40-42B, the bevel gear bushing 4452can be a half ring constructed from a biocompatible titanium alloy orother suitable material. The bevel gear bushing 4452 serves to align thegear output 4444 with the pinion gear 4442, reduce friction, ensure thatthe gear output 4444 is held in place within the housing 4402, andprevent wear between the output gear 4444 and the housing 4402.

The bevel output gear 4444 forms an end (i.e., is integral with) theinternally threaded expansion tube 4404. As a result, the expansion tube4404 rotates with the bevel output gear 4444, thereby translating theexpansion rod 4420 along the longitudinal axis 4401 as the bevel outputgear 4444 rotates, to extend or contract the expansion rod 4420 from orinto the housing 4404 such that the assembly 4400 expands or contractsin length, depending on the direction of rotation of the pinion gear4442.

The bevel gear assembly allows a surgeon to turn the pinion gear 4442,which causes the expandable rod 4420 to extend distally from the housing4402. In an exemplary embodiment, the pinion gear 4442 and the beveloutput gear 4444 are both made of biocompatible titanium alloy (e.g.,TAV), and are designed with a pitch angle such that the pinion gear 4442is able to drive the bevel output gear 4444.

In some embodiments, the bevel gear assembly provides a reduction rationof 0.8:1 or more. In some embodiments, the bevel gear assembly providesa reduction ratio of 1:0.75 such that for every full revolution of thepinion gear 4442, the bevel output gear 4444 rotates 0.75 revolutions.In an exemplary embodiment, the ratio of the pinion teeth to the bevelgear teeth is 15:20. In an exemplary embodiment, the pinion gear 4442 isrotated about one (1) complete revolution to achieve between about 1 mmand 1.25 mm of expansion or contraction of the expansion rod 4420 fromthe housing 4402, with the amount of growth based upon a goal measure of1.8 cm to 2.4 cm per year. Advantageously, a surgeon can fine tune theamount of expansion by either increasing or decreasing the amount ofrotations. This allows the surgeon to expand the expansion rod 4420against large forces caused by the deformity. If a surgeon feels toomuch distraction has been incorporated, the assembly 4400 can be reducedby simply reversing the direction the pinion gear 4442 is turned.

Similar to the assembly 3300 described above, in an exemplaryembodiment, the assembly 4400 is 600 mm long with the expansion rod 4420in a fully retracted position, and 660 mm long with the expansion rod4420 in a fully extended position, allowing for up to 60 mm of growth ofthe patient.

Referring now to FIGS. 43A-43D, a growing rod assembly 5500 (“assembly5500”) in accordance with embodiments of the present disclosure and itsimplantation into a spinal assembly will now be discussed. The assembly5500 advantageously non-invasively increases in length passively withthe use of a ratchet mechanism. Instead of forcing the assembly 5500 tolength (such as required with other growing rods), the assembly 5500will react to tension forces by increasing in length. As such, after theinitial lengthening by the surgeon implanting the assembly 5500 in apatient, the assembly 5500 as the patient stretches. The assembly 5500includes a safety release mechanism in case of overstretching. In someembodiments, the assembly 5500 may be formed of titanium, stainlesssteel, cobalt chrome, or some other biocompatible material that isvisible via MRI.

As depicted in FIGS. 43A-43D, in some embodiments, the assembly 5500includes a fixed rod 5508 and an expansion rod 5520. As used withassembly 5500, the term “proximal” is defined as a direction toward thefree end of the fixed rod 5508 and the term “distal” is defined as adirection toward the free end of the expandable rod 5520. The assembly5500 includes a housing 5502 in the form of a hollow sleeve. A proximalportion 5520A of the expansion rod 5520 includes a plurality of teeth5512 disposed on one side of the expansion rod 5520. In someembodiments, the proximal portion 5520A extends the entire length of thehousing 5502.

In some embodiments, the safety release mechanism discussed aboveincludes a pawl 5510 coupled to the housing 5502. The pawl 5510 isfixedly coupled to the housing 5502 at a proximal end 5510A and has afree end 5510B opposite the proximal end 5510A. As shown more clearly inFIGS. 43B and 43C, the free end 5510B extends into an opening 5507formed in the housing 5502 to engage the teeth 5512 of the expansion rod5520.

As shown more clearly in FIG. 43C, each of the teeth 5512 includes aramped portion 5512A and a vertical portion 5512B. The assembly 5500 isconfigured such that the pawl 5510 allows the expansion rod 5520 to movein the direction indicated by arrow A because the free end 5510B of thepawl 5510 moves along the ramp. However, movement opposite the directionindicated by arrow A is prevented by the abutment of the free end 5510Bof the pawl 5510 and the vertical portion 5512B of the teeth. As aresult, when a patient stretches, the assembly 5500 expands (i.e., theexpansion rod 5520 moves in the direction indicated by arrow A).However, the pawl 5510 prevents collapse of the assembly.

In the event of overexpansion, the safety release mechanism allows adesired amount of collapse of the assembly 5500. To achieve this, adepression 5514 is formed in the housing 5502 beneath the pawl 5510 nearthe free end 5510B, as shown in FIGS. 43B-43D. When the pawl 5510 ispushed into the depression (as depicted in FIG. 43D), the free end 5510Bis moved out of engagement with the teeth 5512, thus allowing for theassembly 5500 to be collapsed a desired amount. The safety mechanismadvantageously allows for the collapsing of the assembly 5500non-invasively by simply pushing down on the patient's skin directlyabove the pawl 5510 until the pawl is pushed into the depression 5514.

In some embodiments, the pawl 5510 may alternative be formed of amaterial having a transition shape so that the pawl is in a releasedconfiguration when heated. As such, if the patient over-lengthens theassembly, heat can be applied to the area above the pawl to release it.The temperature at which such a transition would occur is above bodytemperature but less than a temperature that would cause harm to thepatient.

It is to be understood that the disclosure describes a few embodimentsand that many variations of the invention can easily be devised by thoseskilled in the art. Although the invention has been described in exampleembodiments, those skilled in the art will appreciate that variousmodifications may be made without departing from the spirit and scope ofthe invention. It is therefore to be understood that the inventionsherein may be practiced other than as specifically described. Thus, thepresent embodiments should be considered in all respects as illustrativeand not restrictive. Accordingly, it is intended that such changes andmodifications fall within the scope of the present invention as definedby the claims appended hereto.

What is claimed is:
 1. An implantable growing rod assembly comprising: ahousing; an internally threaded expansion tube mounted inside of thehousing; a fixed rod extending along a longitudinal axis away from thehousing; an expansion rod extendible from the housing along thelongitudinal axis; and a bevel gear assembly disposed in the housing andadapted to translate the expansion rod along the longitudinal axis,wherein the bevel gear assembly includes a bevel pinion gear and a beveloutput gear perpendicular to the bevel pinion gear
 2. The implantablegrowing rod assembly of claim 1, wherein the bevel pinion gear includesteeth that mesh with teeth of the bevel output gear such that rotationof the bevel pinion gear causes rotation of the bevel output gear
 3. Theimplantable growing rod assembly of claim 2, wherein the bevel outputgear is fixed to the internally threaded expansion tube such that theinternally threaded expansion tube rotates with the bevel output gear.4. The implantable growing rod assembly according to claim 1, whereinthe expansion rod comprises a threaded proximal end threadingly engagedwith the internally threaded expansion tube.
 5. The implantable growingrod assembly according to claim 4, wherein the expansion rod comprises adistal end adapted to extend outwardly from the housing.
 6. Theimplantable growing rod assembly according to claim 1, wherein the bevelpinion gear includes teeth at one end.
 7. The implantable growing rodassembly according to claim 1, wherein the bevel gear assembly islocated in a housing cap between the housing and the fixed rod.
 8. Theimplantable growing rod assembly according to claim 7, wherein the bevelpinion gear is disposed in the housing cap between a first pinionbushing and a second pinion bushing.
 9. The implantable growing rodassembly of claim 8, wherein the internally threaded expansion tube isformed of PEEK.
 10. The implantable growing rod assembly of claim 9,further comprising: a wave washer disposed between the housing and oneof the first pinion bushing or the second pinion bushing and configuredto exert a locking force on the bevel pinion gear to prevent undesiredback drive of the bevel pinion gear.
 11. The implantable growing rodassembly of claim 10, wherein the bevel pinion gear includes a firstplurality of teeth at a first end and a second plurality of teeth at asecond end, wherein the first plurality of teeth engages the teeth ofthe bevel output gear to extend the expansion rod, and wherein thelocking force exerted by the wave washer is configured to push thesecond plurality of teeth into engagement with the teeth of the beveloutput gear to lock movement of the bevel output gear and the internallythreaded expansion tube.
 12. The implantable growing rod assemblyaccording to claim 1, further comprising: a keyed bushing located in thehousing and wherein the expansion rod comprises a mating key located inthe keyed bushing such that, as the expansion rod extends from thehousing, the keyed bushing prevents the expansion rod from rotating. 13.The implantable growing rod assembly according to claim 12, wherein thekeyed bushing includes a keyway in the form of a flat surface formedthrough an entire length of the bushing.
 14. An implantable growing rodassembly comprising: a housing; an internally threaded expansion tubemounted inside of the housing, wherein the internally threaded expansiontube is formed of PEEK; a fixed rod extending along a longitudinal axisaway from the housing; an expansion rod extendible from the housingalong the longitudinal axis; and a bevel gear assembly disposed in thehousing and adapted to translate the expansion rod along thelongitudinal axis, wherein the bevel gear assembly comprises: a bevelpinion gear; a first pinion bushing disposed between a first side of thebevel pinion gear and the housing; a second pinion bushing disposedbetween a second side of the bevel pinion gear and the housing; and abevel output gear perpendicular to the bevel pinion gear, wherein thebevel pinion gear includes teeth that mesh with the teeth of the beveloutput gear such that rotation of the bevel pinion gear causes rotationof the bevel output gear.
 15. The implantable growing rod assemblyaccording to claim 14, wherein the expansion rod comprises a threadedproximal end threadingly engaged with the internally threaded expansiontube.
 16. The implantable growing rod assembly according to claim 15,wherein the expansion rod comprises a distal end adapted to extendoutwardly from the housing.
 17. The implantable growing rod assemblyaccording to claim 14, wherein the bevel gear assembly is located in ahousing cap between the housing and the fixed rod.
 18. The implantablegrowing rod assembly of claim 14, wherein the bevel pinion gear includesa first plurality of teeth at a first end and a second plurality ofteeth at a second end, wherein the first plurality of teeth engages theteeth of the bevel output gear to extend the expansion rod, and whereina locking force exerted by a wave washer is configured to push thesecond plurality of teeth into engagement with the teeth of the beveloutput gear to lock movement of the bevel output gear and the internallythreaded expansion tube.
 19. The implantable growing rod assemblyaccording to claim 14, further comprising: a keyed bushing located inthe housing and wherein the expansion rod comprises a mating key locatedin the keyed bushing such that, as the expansion rod extends from thehousing, the keyed bushing prevents the expansion rod from rotating. 20.The implantable growing rod assembly according to claim 19, wherein thekeyed bushing includes a keyway in the form of a flat surface formedthrough an entire length of the bushing.